Introduction

The project calculates the convolution of two vectors, and shows the resulting vector in the MsChart control. The function that performs the convolution is written in MatLab and then through the MatLab Add-in converted to C code ready to be used inside our app.

Requirements

Installing the MatLab Add-in

The add-in automates the integration of M-files into Visual C++ projects. The add-in for Visual Studio is automatically installed on your system when you run either mbuild -setup or mex -setup and select Microsoft Visual C/C++ version 6. In order to use the add-in you must follow these steps:

Start MatLab, in the prompt type mbuild -setup

Follow the menus and choose MS Visual C++6.0.

Type the following commands in the matlab prompt :

cd (prefdir)mccsavepath

These commands save the MatLab path to a file called mccpath in your user preferences directory (prefdir), ussually inside your documents and settings file. The path is used by the add-in because it runs outside Matlab and there is no other way for it to determine your Matlab path. If you add new directories to your Matlab path you will have to rerun this command if you want the add-in to see them.

Configure the Matlab Add-in for Visual Studio 6 to work within MSVisual C++.

Open MSVisualC++.

Select Tools -> Customize from the MSVC menu.

Click on the Add-ins and Macro Files tab.

Check MATLAB for Visual Studio on the Add-ins and Macro Files list and click Close.

The floating MATLAB add-in for Visual Studio toolbar appears. The checkmark directs MSVC to automatically load the add-in when you start MSVC again.

Calculating the convolution in Matlab

We will write a simple function in MatLab that will perform the convolution of two vectors:

In1 and In2 and store the result in out.

We actually can use any matlab built-in function or toolbox function inside our function here we use only the function conv for simplicity.

Writing the Application

Use the MFC AppWizard (exe) option to generate a Dialog Based Application and call it conv. Create a Button which will calculate the convolution of two given vectors.

Add the code below to the button's Message Handler.

//x1 and x2 are the input array to do the computation//res will have the result, we already know that the length //of the convolution of 2 vectors is (length(x1)+length(x2)-1)=19double x1[]={1,2,3,4,5,6,7,8,9,0};
double x2[]={4,5,6,7,4,5,8,9,0,7};
double res[19];
//create the arrays that will be passed to MyFunc
mxArray* In1;
mxArray* In2;
mxArray* Out;
//we make them Real and have 10 values
In1=mxCreateDoubleMatrix(1,10,mxREAL);
In2=mxCreateDoubleMatrix(1,10,mxREAL);
//this make In1=x1;In2=x2
memcpy(mxGetPr(In1),x1,10*sizeof(double));
memcpy(mxGetPr(In2),x2,10*sizeof(double));
//Call to MyFunc.m that return the convolution of In1 and In2
Out=mlfMyFunc(In1,In2);
//now we have the result(Out) in a double array 'res'
memcpy(res,mxGetPr(Out),19*sizeof(double));
//Destroy matrices
mxDestroyArray(Out);
mxDestroyArray(In1);
mxDestroyArray(In2);

Copy MyFunc.m into your VC++ project directory. Now go to the MatLab Add-in and click the .m++ (Add m-files to current project) button:

Then select the MyFunc.m file and click Open. After a while you will see new files added to your project.

Under MATLAB M-files you will see our MyFunc.m, you can even edit it from inside Visual C++. Under MATLAB C/C++ are MyFunc.c and MyFunc_main.c, generated by the MatLab Compiler. And all the headers needed by the compiler.

We can't build the app yet, we must add the following lines to convDlg.cpp:

#include "matlab.h"
#include "MyFunc.h"

Now the project should be built without any problem.

Points of Interest

The steps described here don't include the MSChart part, you can see it from the source code, but you can see that the calculation is done by placing a breakpoint inside the button message handler and checking the value of the resvector after the line:

Well I hope this simple article be interesting for MatLab lovers, this is the first article I wrote, so I apologize if it is not clear enough. I will be glad to explain anything if you ask me. Greetings.

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About the Author

Daniel Cespedes is now working on his final project to get the Electrical Engineering degree at the National University of Technology in Cordoba Argentina. He is developing a Computerized system for the study of Human Echolocation, the ability to detect obstacles with the echoes of self generated sounds.(yes like bats!!) at the CINTRA (Centro de Investigación y Transferencia Acústica).He uses MsVisual C++ 6 as a developing tool. He also work at the Software Research Lab at the University.
He comes from Sta.Cruz de la Sierra-Bolivia a paradise in SouthAmerica´s heart, where you can find pure air, nature contact, happy people, beautiful women etc.

I had matlab 7.0 and the mccsavepath command doesn't work anymore, this is because this version of matlab supposedly 'automatically' adds its path to the windows path. this is not necessarily done right and can be corrected manually. See instructions here and add you matlab bin directory to the path, for example on my computer I copied this to my path:
C:\Program Files\MATLAB\R2007a\bin
C:\Program Files\MATLAB\R2007a\bin\win32

also, make sure your visual c++ bin directory is in the same path, on my computer:
C:\Program Files\Microsoft Visual Studio\Common\MSDev98\Bin

Before I discovered this I reinstalled an older version of matlab that did have a working mccsavepath command, matlab 6.5 (release 13). in matlab 6.5 I typed in the commands as this article shows and they worked ok, but then I still had to go into the windows path and manually make sure that the matlab and vc++ bin directories were in the windows path:
c:\matlab6p5\bin\win32
C:\Program Files\Microsoft Visual Studio\Common\MSDev98\Bin

some of you asked about mlfMyFunc undeclared identifier errors. The way to fix this is to open the myfunc.h file, and look to see what the corrrect capitalization is of the function, it should be around line 26 of the .h file. the capitalization seems to be arbitrary so make sure you check, for me it was mlfMyfunc() even though the .h file was myfunc.h and my m-file function was MyFunc()

/*
this part below is in the OK buttons function
I modified the code posted in the instructions to be simpler
my code sends two numbers, x1 and x2 to the m-file, the m-file
decides which number is larger and sends it back to the c++ code
---
you can see the unmodified original code in the comments above each
line of my modified code
---
In order to see that the code was working correctly, I made an 'edit box'
in my GUI dialog, the variable associated with the edit box is m_Output
So at the end of my code I write the value returned to the c++ code from the
m-file to the edit box so you can see it. In the case of the two numbers I'm
sending the m-file in my code (4 and 6), it should show a 6 when you click the
GUI's ok button to run the program.
*/

I have the same exact proplem as the following and i have matlab R2007b :

I follow the instruction to
Configure the Matlab Add-in for Visual Studio 6 to work within MSVisual C++:
by Open MSVisualC++, Select Tools -> Customize from the MSVC menu.
Clicking on the Add-ins and Macro Files tab.
but i dont see any MATLAB for Visual Studio on the Add-ins or Macro Files list ,
i also type the command in MAATLAB:
cd(prefdir) ;
save mccpath;

sir,
I used the example to build an Vc++6.0 application which use matlab function and yhe application run well. my problem is when i execute my application to the another computer i have some errors. how can i generate the executable file of my application?

i follow the instruction to
Configure the Matlab Add-in for Visual Studio 6 to work within MSVisual C++:
by Open MSVisualC++, Select Tools -> Customize from the MSVC menu.
Clicking on the Add-ins and Macro Files tab.
but i dont see any MATLAB for Visual Studio on the Add-ins or Macro Files list ,
i also type the command in MAATLAB:
cd(prefdir) ;
save mccpath;

I'm new to MATLAB programming. I currently use MATLAB v6.1(R12) on
MS WINXP SP2 with MS Visual C++ (6.0). I created a section of a
program within the Visual C++ environment and inserted a function
M-file into this program using the MATLAB Visual Studio Add-in. The
function M-file is to produce graphical output based on the values of
arrays which are to be initialized in the C++ environment. The
resulting program shows no compile errors.

The problem begins when the program is executed. It seems unable to
use the arrays intialized within the Visual C++ environment and
returns the error: "variable x is undefined". I don't understand why
this is so as the arrays have been initialized and passed
(mwArray(n_,_n,_name). I would appreciate it if someone could
provide assistance urgently.

I'm new to MATLAB programming. I currently use MATLAB v6.1(R12) on
MS WINXP SP2 with MS Visual C++ (6.0). I created a section of a
program within the Visual C++ environment and inserted a function
M-file into this program using the MATLAB Visual Studio Add-in. The
function M-file is to produce graphical output based on the values of
arrays which are to be initialized in the C++ environment. The
resulting program shows no compile errors.

The problem begins when the program is executed. It seems unable to
use the arrays intialized within the Visual C++ environment and
returns the error: "variable x is undefined". I don't understand why
this is so as the arrays have been initialized and passed
(mwArray(n_,_n,_name). I would appreciate it if someone could
provide assistance urgently.

On VS2003 I get mbuild -setup and mex- setup to work and can build mex files (from .c/.cpp code and .m code). I did this (in case anyone wants to know) by making a copy of the VC folder in the visual studio .net folder and naming it Vc7 (as this is where matlabs mbuild -setup script looks for the cl.exe compiler).
I could also get the Visulal Studio. However the add-in, that should be made availeble after running the mbuild -setup, is not availeble because the tools-customize dialogue is not the same as in VC++ 6. Also the (copied) Vc7 folder is not accessed by VS2003 .net so, if this is where the add-in is placed it will not be found.
To overcome this I used the MatLab VS.Net Custom App Wizard (see matlab exchange) to allow me to start a mex project using the VS IDE new project wizard. This was fine.

Now I have upgraded to VS2005 and things are not so good.

On VS2005 I can get the mex -setup and mbuild -setup scripts to run successfully (by doing the same copying <vc> and calling it <vc7> trick) but this time the .dlls dont work. Also I have tried the MatLab VS.Net Custom App Wizard and although I can get the wizard to create the project, the project no longer compiles.

If anyone has sorted this out yet please let me know. Also, if your using VS2003 then try my trick of creating the Vc7 folder in the VS.NET2003 folder.

I want to write a Visual C++ program which gets data from the user and gives this data to GAMS (on a simple button click and GAMS should not run visibly). GAMS is then supposed to make a calculation and give the obtained data back to my Visual C++ program so that I can use this new data. Does anybody know if this is possible???? And if so, then how should I do this? THANKSA in advance.